Grading of coronary artery stenosis requires grading based on coronary angiography. Grade I is the mildest and is a mild plaque infiltration, with stenosis below 25%. Grade II stenosis is 26%-50%. Grade III as well as grade IV are coronary artery disease, with grade III stenosis being 50%-75% and grade IV stenosis being 75% to complete occlusion. If the stenosis is less than 50%, it is considered coronary atherosclerosis. Coronary angiography is the gold standard for the diagnosis of coronary artery disease. If coronary angiography shows that a patient has coronary artery disease with a stenosis greater than 75%, then coronary intervention is recommended.